Party inspectors say his influence lingers in the Chinese megacity he once governed, which doesn't bode well for a Bo successor

Five years after former Communist Party bigwig Bo Xilai saw his ambitions for high office spectacularly quashed by scandal, party inspectors say his “pernicious influence” lingers in the Chinese megacity he once governed.

Their verdict doesn’t don’t bode well for a Bo successor whose own chances for promotion into China’s top leadership depended in large part on how he overcomes Mr. Bo’s legacy in Chongqing–a time marked by a Maoist revival and heavy state spending, and bookended by dramatic revelations of corruption and murder.

Sun Zhengcai, who became Chongqing party secretary in late 2012, hasn’t gone far enough in his efforts to clean up the city’s bureaucracy and restore institutional discipline, according to findings published Monday by the party’s top disciplinary watchdog.

Corruption remained rife in Chongqing’s state-owned enterprises while some officials still waver in their adherence to the party leadership and fall foul of frugality rules, the Central Commission for Discipline Inspection said.

Most damningly, the agency faulted municipal leaders for failing to thoroughly erase the influence of Mr. Bo and his onetime police chief, Wang Lijun–whose flight to the U.S. Consulate in Chengdu in February 2012 precipitated Mr. Bo’s downfall and touched off one of China’s largest political dramas in decades.

Messrs. Bo and Wang are in prison for corruption and abuse of power, and Mr. Bo’s wife, Gu Kailai, is serving a de facto life sentence for the murder of a British businessman. All three have since become hate figures under President Xi Jinping’s signature anticorruption campaign, and any association with them is fraught with political danger, observers say.

The CCDI statement — and the invocation of Mr. Bo’s name — could jeopardize Mr. Sun’s chances of promotion into the highest tier of party leadership at a leadership shuffle later this year, said Wu Qiang, a Beijing-based researcher and former political-science lecturer at Tsinghua University.

Mr. Sun already holds a seat in the 25-member Politburo, and many party insiders have seen him as a strong contender for the Politburo Standing Committee, the inner sanctum of Chinese political power, or even as a possible successor to Mr. Xi.

Since taking the reins of the party in late 2012, Mr. Xi has directed a withering crackdown on graft and political disloyalty–using the party’s disciplinary apparatus to quash resistance against his agenda.

Some party insiders say Mr. Xi may now be trying to block promotion of a potential successor at the party congress later this year, a move that would help him remain in office after his second term expires in 2022.

“Disciplinary agencies are being used as tools to ensure political loyalty,” said Mr. Wu, the Beijing-based researcher. “Factional struggles within the party have taken the form of these apparently politicized disciplinary inspections.”

The CCDI statement came as Mr. Xi urged the party elite to implement new disciplinary measures rolled out in October. Senior cadres must “grasp the correct political direction” and “show strict political discipline,” state media quoted Mr. Xi as telling party officials gathered Monday at the Central Party School in Beijing.

Mr. Xi’s campaign, however, has stirred public blowback against disciplinary efforts deemed as going too far.

In one case last week, an industrial-park employee in the central province of Hunan was censured for “drinking milk in the office at 9 a.m.,” according to local media, though local officials later said the employee was scolded for having breakfast and surfing the Web while on the clock.

Last month, a nurse at a state-run hospital in the southwestern city of Guiyang had three months’ worth of performance bonuses revoked after being seen playing mahjong–a popular tile-based game–at a local restaurant, in what officials deemed as a public display of frivolity.

The discipline inspectors in both cases were savaged on social media. On Monday, the Communist Party’s flagship newspaper, People’s Daily, weighed in by criticizing what it described as misguided enforcement of discipline.

“If mountains get made out of molehills, and accountability is wantonly demanded,” the newspaper says, “this could generate fresh disharmony and damage the credibility of the system.”